20Y-27-21190 Final Drive Sun Gear 21T for Komatsu PC200-6 Excavator

20Y-27-21190 Final Drive Sun Gear

The 20Y-27-21190 sun gear is used in the planetary reduction section of selected Komatsu excavator final drives. Its position at the center of the planetary gear set allows rotational input to be transferred into the surrounding gears as the travel gearbox reduces speed and increases output torque.

Because this gear works continuously under tooth contact and torsional load, correct tooth profile and bore alignment are important for stable engagement throughout the reduction stage.

For older Dash-6 excavators, identification should be based on the original final drive configuration rather than machine model alone, especially when the travel gearbox may have been replaced during previous repairs.

Why the Center Gear Deserves Close Inspection

A sun gear carries load through every tooth engagement with the surrounding planetary gears. Small changes in tooth shape or alignment can therefore influence several contact points at the same time.

If the original gear has developed uneven wear, simply installing another gear without checking the rest of the reduction stage may not correct the underlying problem.

The mating gears, carrier support and lubrication condition should be evaluated together whenever abnormal tooth damage is found.

What the Wear Pattern Can Tell You

The condition of the original sun gear can provide useful clues about the health of the travel gearbox:

• Pitting across the working tooth surfaces can indicate prolonged contact fatigue

• Chipped tooth edges may indicate impact loading or excessive backlash

• Wear concentrated on one side of the teeth may suggest poor alignment

• Scoring inside the center bore can indicate abnormal movement or support wear

• Blue or dark discoloration can indicate excessive heat

• Metal particles in the gearbox oil may indicate wider internal gear damage

When several of these conditions appear together, the complete reduction stage should be inspected before reassembly.

Do Not Identify a Sun Gear by Tooth Count Alone

Tooth count is useful for identification, but it should not be the only matching point. Similar excavator final drives can use gears that look nearly identical while differing in bore size, overall width, tooth geometry or gearbox position.

For a reliable match, compare the original gear together with the final drive configuration and machine serial information.

This extra check is especially useful when working on older machines where the installed travel gearbox may no longer be the original factory unit.

Information to Send for Fitment Checking

If you need help identifying the correct replacement gear, send the following information with your inquiry:

• Excavator model and machine serial number

• Final drive or travel gearbox information

• Clear front and side photos of the original sun gear

• Confirmed tooth count

• Outside diameter and center bore diameter

• Overall gear width or height

These details allow the replacement gear to be compared with the original component before shipment.

Final Drive Gear Support from Topvelsun

Topvelsun supplies replacement gears and other travel reduction components for excavator final drive repair and parts distribution.

Send us part number 20Y-27-21190 together with your machine and original gear information, and we can help verify the application before quotation.